In general, body armor must provide protection to the user, while at the same time not unduly hindering the movements of the user and not requiring the user to carry unreasonably excess weight. In addition, it is often important that body armor be concealable, so that enemy combatants, terrorists, criminals, or other antagonists are not prompted to selectively direct their attacks toward unprotected parts of the body.
These requirements can significantly limit the use of body armor, and the degree of protection that acceptable body armor can provide. In particular, concealable body armor is typically not adequate for protecting foot soldiers in combat. A standard test often used to simulate hand-weapon threats from terrorists and enemy soldiers is an impact from a round nose, 124 grain, 9 mm “full metal jacket” (“FMJ”) projectile traveling at 1000 feet-per-second or faster. Conventional torso armor provided by the military for protection against such threats is not typically concealable, since it tends to create a visible bulge that can be easily detected by antagonists. In addition, these solutions cannot be extended to the arms and legs of a foot soldier without significantly limiting the user's freedom of movement and burdening the user with excess weight.
For military applications, the carry loads for modern infantry and tactical operations are so high that additional extremity protection is only used under very limited circumstances. In general, the current approach to extremity protection is to model the extremity protective panels after the fabric panels found in the ballistic vest. This approach leads to a typical weight of 0.5-1 lb/ft2 (72-144 oz/yd2), and a thickness of up to 2 cm and more.
One promising approach to providing flexible, thin, lightweight body armor is to bond tiles made from rigid, protective materials such as metals and/or ceramics to a support fabric. The tiles are bonded in a nearly continuous, adjoining mosaic pattern. Examples are disclosed in U.S. Pat. No. 7,393,588 and US publication 2008-0104735 A1, previously filed by the present inventor, and incorporated herein by reference for all purposes.
However, until the present invention such mosaic armor systems only demonstrated good projectile protection when the thickness of the tiles was at least roughly equal to the thickness of the projectile. The accepted wisdom in the art at the time of the present invention regarding the most effective configurations for hard armor is illustrated by the work on penetration mechanics by Anderson and Walker (see for example Int. J. Impact Engng Vol. 11, No. 4, 1991, pp 481-501, Int. J. Impact Engng Vol. 14, No. 1-4, 1993, pp 1-12, and Int. J. Impact Engng Vol. 16, No. 1, pp. 19-48, 1995, incorporated herein by reference for all purposes). Before the present invention, the inventor collaborated with Dr. Anderson of Southwest Research Institute (SwRI) on ceramic mosaic designs. In this work, the armor models from SwRI and our ballistic testing demonstrated that hard armor thickness should be roughly equal to the caliber of the projectiles. For 7.62 mm caliber weapons, ceramic armor performed best when it had a thickness of at least 7 mm. The penetration mechanics showed that this 1:1 ratio was the transition between bending and plug-failure modes in armor.
In other tests, steel tiles having a thickness of 9 mm provided V50 performance for a round nose, 124 grain, 9 mm “full metal jacket” (“FMJ”) projectile traveling at 1000 feet-per-second or faster, but the V50 performance declined rapidly as the thickness of the tiles fell below 9 mm. Unfortunately, mosaic armor fashioned from 9 mm thick steel or ceramic tiles is impractical for many applications because of the weight of the tiles and the difficulty of concealing such thick tiles.
A body armor assembly is therefore needed which can be used for constructing concealable body armor which is sufficiently flexible, light in weight, and thin so as to be worn for extended periods without undue weight burden, and without undue restriction of a user's movements, while protecting the user against typical threats from military and terrorist “assault” weapons, such as a 9 mm projectile traveling at 1000 feet-per-second or faster.